1. Field of the Invention
The present invention relates to a technique for displaying a still image according to a still image coding method and a moving image according to a moving image coding method.
2. Description of the Related Art
Some image recording apparatuses such as digital video cameras use a digital versatile disc (DVD) as a recording medium to record a still image and a moving image thereon. Such an image recording apparatus can separately and individually record a moving image and a still image on the same recording medium.
In addition, the image recording apparatus, in recording a moving image, encodes a moving image using a Moving Picture Experts Group (MPEG) method as a coding method. The image recording apparatus records the encoded moving image on a DVD according to a format such as DVD-Video format or DVD Video Recording format.
In recording a still image, the image recording apparatus records a still image using a Joint Photographic Experts Group (JPEG) method as a coding method. The image recording apparatus records the encoded still image according to a format such as Exchangeable image file format (Exif) or Design rule for Camera File system (DCF) format.
As described above, in an image recording apparatus, mutually different coding methods and recording formats are used for recording a moving image and a still image, respectively. Accordingly, in order to reproduce both a moving image and a still image, it is necessary that an image reproduction apparatus corresponding to the image recording apparatus is compliant with both coding methods and both recording formats. That is, it is necessary that the image reproduction apparatus include decoders (decoding unit) compliant with both the MPEG coding method and the JPEG coding method.
Accordingly, a reproduction apparatus, such as a conventional DVD player, which includes only an MPEG decoder, can reproduce a moving image portion but is incapable of reproducing a still image from a recording medium having the still image recorded thereon.
Japanese Patent Application Laid-Open No. 2004-201170, Japanese Patent Application Laid-Open No. 2004-297229, and Japanese Patent Registration No. 3551181 discuss a method for encoding a still image into a moving image compliant with the MPEG coding method by converting a still image encoded by the JPEG coding method into an I (intra) picture defined by the MPEG coding method. This method enables a conventional image reproduction apparatus to reproduce a still image as a moving image compliant with the MPEG coding method.
However, the following problem arises in displaying a still image as an MPEG-coded moving image.
That is, in generating an MPEG-coded moving image according to a DVD format, there is a restriction on the resolution of a moving image. Even the maximum resolution of a moving image is lower than the resolution of a still image generated by an image recording apparatus. Accordingly, in converting a still image into a moving image, it is necessary to lower the resolution of a high-resolution still image down to a resolution equivalent to the resolution of a moving image. Thus, the image quality of a still image degrades. In addition, there is a restriction on a bit rate for a moving image according to a DVD format, which also causes the image quality to degrade.
If an image reproduction apparatus is equipped with both reproduction functions according to the MPEG coding method and the JPEG coding method, a JPEG-coded still image, which corresponds to a low-quality MPEG-coded moving image displayed by a user, can be identified and acquired to be displayed at a high-image quality. However, in the case where the user does not desire to display the still image in that way, that function is not useful considering a user's convenience. In addition, in that case, an operation performed for displaying the still image may become too complicated for the user.